This invention relates to novel adhesive compositions.
Alpha-cyanoacrylates are known to be useful in bonding operations involving a variety of substrates. Alpha-cyanoacrylates are generally convenient to use as adhesives since they polymerize rapidly (e.g., often setting within about 30 seconds) at room temperature when exposed to the small amounts of moisture typically found on the surfaces of the substrates being bonded.
Unfortunately, alpha-cyanoacrylates have their limitations. For example, alpha-cyanoacrylates, once cured, may exhibit decreased performance when exposed to water or humid environments. Also, alpha-cyanoacrylates may exhibit poor heat resistance and may provide inadequate peel and impact strengths.
The shortcomings of alpha-cyanoacrylates as adhesives have been recognized in the prior art and there have been efforts in developing new monomers for use as adhesives. U.S. Pat. No. 3,316,227 (Gerber), for example, discloses alkyl 2-cyanopenta-2,4-dienoates which are said to be useful as adhesives. These monomers, however, polymerize slowly at room temperature (e.g., often requiring an hour or more for suitable cure) and, therefore, are not useful by themselves as rapid-curing adhesives. Furthermore, these monomers are solids at room temperature, thereby rendering them impractical to handle in most adhesive applications.
U.S. Pat. No. 3,554,900 (Quinn et al.) discloses alkenyl and alkoxyalkyl esters of 2-cyanopenta-2,4-dienoic acid which, when employed either alone or in combination with alpha-cyanoacrylates, exhibit improved impact strengths upon curing. Unfortunately, as with the above-mentioned alkyl 2-cyanopenta-2,4-dienoate adhesives, these monomers also generally polymerize slowly at room temperature.
United Kingdom Pat. No. 1,415,102 (Trofimov et al.) discloses adhesive compositions comprising an alpha-cyanoacrylate and a bis-ester of 2-cyanopenta-2,4-dienoic acid. These compositions are said to exhibit improved heat resistance due to the presence of the latter bifunctional compound which provides for crosslinking of the polymer network.